On about 5 to 10% of ADS1120 we are using the DRDY pin (pin 12) does not go low after power-up as specified in the data sheet. We are using this pin to detect when the device is ready. Below is a part of the circuit diagram and two traces. The first trace shoes what happens with a devices that is noy workin and the second trace a working device.
The traces are: Yellow trace = DVdd (3V); Blue trace = SCLK; Purple trace = DRDY (pin 12); Green trace = CS.
Regards
Richard Fenton